The present invention relates to a method for the cosmetic treatment of a keratin material comprising at least the steps of: (a) having available a lyophilizate containing at least one live or inactivated, physiologically acceptable microorganism, one of its metabolites or one of its fractions and at least one surfactant with an HLB greater than or equal to 12, (b) having available a physiologically acceptable medium, separate from the said lyophilizate, (c) bringing the said lyophilizate extemporaneously into contact with the said medium under conditions favorable for the solubilization and/or dispersion of the said lyophilizate in the said medium, and (d) bringing the mixture obtained in the preceding step into contact with the said keratin material. It further relates to a lyophilizate as defined above.
